Revision as of 17:57, 24 July 2012

Flow in a 3D diffuser

Confined flows

Underlying Flow Regime 4-16

Abstract

The incompressible flow developing fully in a three-dimensional duct and then expanding into a diffuser, whose upper wall and one side wall are appropriately deflected, has been investigated experimentally (Cherry et al., 2008, 2009) and computationally by means of DNS (Direct Numerical Simulation; Ohlsson et al., 2009, 2010), LES (Large-Eddy Simulation) as well as by different hybrid LES/RANS and RANS (Reynolds-Averaged Navier- Stokes) models. The results of the computational studies were analysed along with the experimental reference database in the framework of two workshops on "Refined Turbulence Modelling" (Steiner et al., 2009 and Jakirlic et al., 2010) organized by the ERCOFTAC Special Interest Group on Turbulence Modelling (SIG15). Two three-dimensional diffuser configurations differing in terms of the values of the expansion angles - the upper-wall expansion angle is reduced from 11.3o (diffuser 1) to 9o (diffuser 2); the side-wall expansion angle is increased from 2.56o (diffuser 1) to 4o (diffuser 2) - were considered. These slight modifications in the diffuser geometry led to substantial changes in the flow structure with respect to the onset, location, shape and size of the three-dimensional separation pattern associated with the corner separation and corner reattachment, Fig. 1. The inflow in both considered cases is characterized by a Reynolds number Reh=10000, based on the inlet duct height.

Contributed by: Suad Jakirlic — Technische Universität Darmstadt